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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling
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Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

机译：12900年前的外星撞击证据，导致巨型动物的灭绝和年轻树妖的降温

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摘要

A carbon-rich black layer, dating to ≈ 12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≌12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (ⅰ) magnetic grains with iridium, (ⅱ) magnetic microspherules, (ⅲ) charcoal, (ⅳ) soot, (ⅴ) carbon spherules, (ⅵ) glass-like carbon containing nanodiamonds, and (ⅶ) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.
机译：早先在北美约50个克洛维斯时代的地点发现了一个富含碳的黑色层，其历史可追溯到≈12.9 ka，并与年轻的树妖（YD）突然降温同时出现。灭绝的更新世大型动物的原位骨骼以及Clovis工具组合出现在该黑色层以下，但不在其内部或上方。灭绝，YD冷却和克洛维斯培养终止的原因长期以来一直存在争议。在本文中，我们为for12.9 ka发生的外星（ET）影响事件提供了证据，我们假设该事件引起了突然的环境变化，从而导致了YD降温，重大的生态重组，大规模的灭绝以及最终人类的快速行为转变克洛维斯时期。北美克洛维斯时代的站点覆盖着一层薄而离散的层，该层具有（peak）带有铱的磁性颗粒，（ⅱ）磁性微球，（ⅲ）木炭，（ⅳ）烟灰，（ⅴ）碳球的峰值丰度变化（ⅵ）含有玻璃状碳的纳米金刚石，和（ⅶ）带有ET氦气的富勒烯，所有这些都证明了ET的影响以及相关生物量在≈12.9ka时燃烧。该层还延伸到至少15个卡罗来纳州海湾，这些海湾是独特的椭圆形凹陷，其面向大西洋的整个西北沿海平原。我们建议在北美北部上空爆炸一个或多个大型低密度ET对象，这部分破坏了Laurentide冰盖的稳定性并引发了YD冷却。冲击波，热脉冲以及与事件相关的环境影响（例如，大量的生物质燃烧和食物限制）导致了末端更新世大型动物的灭绝和北美古美洲人的适应性转变。

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